Acoustic Shunt and Method of Attenuating Noise Generated in a Heater Venting System

ABSTRACT

A heater venting system comprises an exhaust blower, an exhaust pipe, and an acoustic shunt. An exhaust passageway of the exhaust pipe is in fluid communication with the blower discharge. The acoustic shunt includes a pipe section having a shunt chamber of a shunt chamber length. The shunt is coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway such that the shunt chamber extends generally laterally from the exhaust passageway. The shunt chamber length is sized to attenuate the noise of the heater venting system.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

APPENDIX

Not Applicable.

BACKGROUND OF THE INVENTION Field of the Invention

This invention pertains to attenuating noise in a heater venting system.

SUMMARY OF THE INVENTION

One aspect of the present invention is a method of attenuating noise generated in a heater venting system. The heater venting system comprises an exhaust blower and an exhaust pipe. The exhaust pipe at least in part defines an exhaust passageway. The method comprises integrating a shunt in the heater venting system. The shunt includes a pipe section having a shunt chamber. The shunt chamber has an open end, a closed end, and a shunt chamber length extending from the open end to the closed end. The shunt is coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber extends generally laterally from the exhaust passageway. The shunt chamber length is sized to attenuate the noise of the heater venting system.

Another aspect of the present invention is a method of attenuating noise generated in a heater venting system. The heater venting system comprises an exhaust blower and an exhaust pipe. The exhaust pipe at least in part defines an exhaust passageway. The method comprises inducing a user to integrate a shunt in the heater venting system. The shunt includes a pipe section having a shunt chamber. The shunt chamber has an open end, a closed end, and a shunt chamber length extending from the open end to the closed end. The shunt is coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber extends generally laterally from the exhaust passageway. The shunt chamber length is sized to attenuate the noise of the heater venting system.

Another aspect of the present invention is a heater venting system comprising an exhaust blower, an exhaust pipe, and an acoustic shunt. The exhaust blower has a blower discharge. The exhaust pipe at least in part defines an exhaust passageway. The exhaust passageway is in fluid communication with the blower discharge. The acoustic shunt includes a pipe section having a shunt chamber. The shunt chamber has an open end, a closed end, and a shunt chamber length extending from the open end to the closed end. The shunt is coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber extends generally laterally from the exhaust passageway. The shunt chamber length is sized to attenuate the noise of the heater venting system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an embodiment of a heater venting system of the present invention, the heater venting system including first and second acoustic shunts.

FIG. 2 is an enlarged schematic view of the first acoustic shunt of the heater venting system of FIG. 1.

FIG. 3 is a schematic view of a second embodiment of an acoustic shunt of the present invention.

FIG. 4 is a schematic view of a third embodiment of an acoustic shunt of the present invention.

Reference numerals in the written specification and in the drawing figures indicate corresponding items.

DETAILED DESCRIPTION

An embodiment of a heater venting system of the present invention is indicated generally by reference numeral 20 in FIG. 1. The heater venting system 20 comprising an exhaust blower 22, an exhaust pipe 24, a first acoustic shunt 26, and a second acoustic shunt 28. The exhaust blower 22 exhausts furnace gasses from a furnace 30 through the exhaust pipe 24. The exhaust blower 22 has a blower discharge 32. The exhaust pipe 24 of the present embodiment comprises a plurality of pipe components, e.g., straight pipe components, elbows, etc. It is to be understood that the number and types of pipe components employed will vary from application to application. The pipe components of the exhaust pipe 24 at least in part define an exhaust passageway 34. The exhaust passageway 34 is in fluid communication with the blower discharge 32.

Referring to FIGS. 1 and 2, the first acoustic shunt 26 includes a first pipe section 40 having a first shunt chamber 42. The first pipe section 40 may be of a single pipe component or may be portions of a plurality of pipe components. The first shunt chamber 42 has an open end 42 a, a closed end 42 b, and a shunt chamber length 42 c extending from the open end to the closed end. In the present embodiment, the first pipe section 40 may be a portion of a pipe tee with a capped end, or the combination of a portion of a pipe tee and a short straight pipe with a capped end. The first acoustic shunt 26 is coupled to the exhaust pipe 24 such that the first shunt chamber 24 is in fluid communication with the exhaust passageway 34 via the open end 42 a of the first shunt chamber 24 and such that the first shunt chamber extends generally laterally from the exhaust passageway. Preferably, the first shunt 26 is positioned such that the closed end is above the open end to prevent liquid from collecting in the shunt. The first shunt 26 may be integrated into the exhaust pipe 24 by replacing an elbow with tee.

The shunt chamber length 42 c is sized to attenuate the noise of the heater venting system. The purpose of the shunt chamber 42 is to create a reflected wave to attenuate an objectionable tone frequency in the heater venting system 20. Under ideal conditions a reflected wave could cancel the objectionable tone frequency if the shunt length 42 c is precisely one-fourth that of the wavelength of the objectionable tone frequency. Under typical conditions, total cancellation of the objectionable tone frequency is not realistic. The shunt length 42 c is unlikely to be precisely one-fourth that of the wavelength since the speed of sound, the velocity of air in the exhaust vent and the steady state running speed of the exhaust blower 22 will vary or not be exactly known. As long as the shunt length 42 c is within 10% of the ideal length, however, an attenuation of the objectionable tone frequency of at least 10 dB per shunt can be realized. In other words, to attenuate the objectionable tone, the first shunt 26 is adjusted such that the shunt chamber length 42 c is nλ/4±0.1(λ/4), where n is any odd integer and A is the wavelength of the objectionable tone. Preferably, the first shunt 26 is adjusted such that the shunt length 42 c is less than ten inches, and more preferably is less than six inches. The first shunt 26 and the exhaust pipe 24 may be of conventional pipe components and of conventional materials, e.g., PVC.

The shunt chamber length 42 c may be selected based on characteristics and operational conditions of the exhaust blower 22. The exhaust blower 22 includes a fan 46 having a plurality of fan blades 46 a, and a motor 48 adapted to rotate the fan. The first shunt 26 may be adjusted such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ=(S+V)/F, where S is the speed of sound in air, V is the air velocity in the exhaust passageway 34, and F is the fan blade pass frequency when the motor 48 is rotating the fan 46 at an operational speed.

Referring again to FIG. 1, the second shunt 28 may be of a construction similar to that of the first shunt 26. The second shunt 28 including a second pipe section 50 having a second shunt chamber 52. The second shunt chamber 52 has an open end, a closed end, and a shunt chamber length 52 c extending from the open end to the closed end of the second shunt 28. The second shunt 28 is coupled to the exhaust pipe 24 such that the second shunt chamber 52 is in fluid communication with the exhaust passageway 34 via the open end of the second shunt chamber and such that the shunt chamber of the second shunt extends generally laterally from the exhaust passageway.

The shunt chamber length 52 c of the second shunt 28 is of a length different from the shunt chamber length 42 c of the first shunt 26 to attenuate a noise of a frequency different from the noise attenuated by the first shunt. If the tone desired to be attenuated by the second shunt is a second harmonic of the objectionable tone attenuated by the first shunt 26, then the second shunt 28 is adjusted such that the shunt chamber length 52 c of the second shunt is nλ/8±0.1(λ/8), where n is any odd integer and λ is the wavelength of the objectionable tone attenuated by the first shunt 26.

Another embodiment of a shunt is indicated by reference number 126 in FIG. 3. The shunt 126 includes a shunt chamber length 142 c. The shunt 126 of FIG. 3 is similar to the shunt 26 of FIGS. 1 and 2, except the shunt 126 is integrated into what would have otherwise been a straight pipe portion of exhaust pipe 24. Thus, except as noted herein, the description above with respect to the shunt 26 of FIGS. 1 and 2 is equally applicable to the shunt 126 of FIG. 3.

Another embodiment of a shunt is indicated by reference number 226 in FIG. 4. The shunt 226 includes a threaded tubular portion 226 a and a threaded plug 226 b sized and configured to threadable mate with the tubular portion. The shunt chamber length may be adjusted by turning the plug 226 b relative to the tubular portion 226 a. Alternatively, the tubular portion and the plug may be unthreaded, with the plug slidable within the tubular portion. Except as noted herein, the description above with respect to the shunt 26 of FIGS. 1 and 2 is equally applicable to the shunt 226 of FIG. 4.

Referring again to FIGS. 1 and 2, in operation, a user integrates or is induced to integrate the first and second shunts 26, 28 into a heater venting system 20 by replacing portions of the exhaust pipe 24 with the shunts as described above. The inducing of a user to integrate a shunt in the heater venting system preferably comprises providing instructions sufficient to cause the user to integrate the shunt in the heater venting system.

As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.

It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, each of the terms “portion” and “section” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed. 

1. A method of attenuating noise generated in a heater venting system, the heater venting system comprising an exhaust blower and an exhaust pipe, the exhaust pipe at least in part defining an exhaust passageway, the method comprising: integrating a shunt in the heater venting system, the shunt including a pipe section having a shunt chamber, the shunt chamber having an open end, a closed end, and a shunt chamber length extending from the open end to the closed end, the shunt being coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber extends generally laterally from the exhaust passageway, manually adjusting the shunt to a shunt chamber length that attenuates noise within the heater venting system; the shunt being adapted such that the shunt chamber length remains unchanged until a user manually changes the shunt chamber length.
 2. A method as set forth in claim 1 wherein the noise includes an objectionable tone, and wherein the step of manually adjusting the shunt comprises manually adjusting the shunt to a shunt chamber length which attenuates the objectionable tone by at least ten decibels.
 3. A method as set forth in claim 2 wherein the shunt is adjusted such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ is the wavelength of the objectionable tone.
 4. A method as set forth in claim 2 wherein the exhaust blower includes a fan having a plurality of fan blades, and a motor adapted for rotating the fan, and wherein the shunt is adjusted such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ=(S+V)/F, where S is the speed of sound in air, V is the air velocity in the exhaust passageway, and F is the fan blade pass frequency when the motor is rotating the fan at an operational speed.
 5. A method as set forth in claim 1 wherein the noise includes an objectionable tone, and wherein the shunt is positioned in a manner such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and A is the wavelength of the objectionable tone.
 6. A method as set forth in claim 1 wherein the exhaust blower includes a fan having a plurality of fan blades, and a motor adapted for rotating the fan, and wherein the shunt is positioned such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ=(S+V)/F, where S is the speed of sound in air, V is the air velocity in the exhaust passageway, and F is the fan blade pass frequency when the motor is rotating the fan at an operational speed.
 7. A method as set forth in claim 1 wherein the integrating of the shunt includes positioning the shunt such that the closed end is above the open end to prevent liquid from collecting in the shunt.
 8. A method of attenuating noise generated in a heater venting system, the heater venting system comprising an exhaust blower and an exhaust pipe, the exhaust pipe at least in part defining an exhaust passageway, the method comprising: integrating a first shunt in the heater venting system, the first shunt including a pipe section having a shunt chamber, the shunt chamber of the first shunt having an open end, a closed end, and a shunt chamber length extending from the open end to the closed end, the first shunt being coupled to the exhaust pipe such that the shunt chamber of the first shunt is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber of the first shunt extends generally laterally from the exhaust passageway, integrating a second shunt in the heater venting system, the second shunt including a pipe section having a shunt chamber, the shunt chamber of the second shunt having an open end, a closed end, and a shunt chamber length extending from the open end to the closed end of the second shunt, the second shunt being coupled to the exhaust pipe such that the shunt chamber of the second shunt is in fluid communication with the exhaust passageway via the open end of the shunt chamber of the second shunt and such that the shunt chamber of the second shunt extends generally laterally from the exhaust passageway, the shunt chamber length of the first shunt being of a first length to attenuate a first noise of a first frequency, the shunt chamber length of the second shunt being of a second length to attenuate a second noise of a second frequency, the second length being different from the first length, the second frequency being different from the first frequency.
 9. A method of attenuating noise generated in a heater venting system, the heater venting system comprising an exhaust blower and an exhaust pipe, the exhaust pipe at least in part defining an exhaust passageway, the method comprising inducing a user to: integrate a shunt in the heater venting system, the shunt including a pipe section having a shunt chamber, the shunt chamber having an open end, a closed end, and a shunt chamber length extending from the open end to the closed end, the shunt being coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber extends generally laterally from the exhaust passageway, manually adjusting the shunt to a the shunt chamber length which attenuates noise within the heater venting system, the shunt being adapted such that the shunt chamber length remains unchanged until a user manually changes the shunt chamber length.
 10. A method as set forth in claim 9 wherein the step of inducing a user to integrate a shunt in the heater venting system comprises providing instructions sufficient to cause the user to integrate the shunt in the heater venting system.
 11. A heater venting system comprising: an exhaust blower having a blower discharge; and an exhaust pipe, the exhaust pipe at least in part defining an exhaust passageway, the exhaust passageway being in fluid communication with the blower discharge; an acoustic shunt including a pipe section having a shunt chamber, the shunt chamber having an open end, a closed end, and a shunt chamber length extending from the open end to the closed end, the shunt having a threaded tubular portion and a threaded plug sized and configured to threadably mate with the tubular portion, the shunt being adapted such that the shunt chamber length may be adjusted by turning the plug relative to the tubular portion, the shunt being coupled to the exhaust pipe such that the shunt chamber is in fluid communication with the exhaust passageway via the open end of the shunt chamber and such that the shunt chamber extends generally laterally from the exhaust passageway, the shunt chamber length being sized to attenuate the noise of the heater venting system.
 12. A heater venting system as set forth in claim 11 wherein the noise includes an objectionable tone, and wherein the shunt is adapted and configured to attenuate the objectionable tone by at least ten decibels.
 13. A heater venting system as set forth in claim 12 wherein the shunt is adapted and configured to facilitate changing of the shunt chamber length.
 14. A heater venting system as set forth in claim 13 wherein the noise comprises an objectionable tone, and wherein the shunt is adjustable to a position in which the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and A is the wavelength of the objectionable tone.
 15. A heater venting system as set forth in claim 13 wherein the exhaust blower includes a fan having a plurality of fan blades, and a motor adapted for rotating the fan, the shunt being adjustable to a position in which the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ=(S+V)/F, where S is the speed of sound in air, V is the air velocity in the exhaust passageway, and F is the fan blade pass frequency when the motor is rotating the fan at an operational speed.
 16. A heater venting system as set forth in claim 12 wherein the noise includes an objectionable tone, and wherein the shunt is positioned in a manner such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ is the wavelength of the objectionable tone.
 17. A heater venting system as set forth in claim 12 wherein the exhaust blower includes a fan having a plurality of fan blades, and a motor adapted for rotating the fan, the shunt being positioned such that the shunt chamber length is nλ/4±0.1(λ/4), where n is any odd integer and λ=(S+V)/F, where S is the speed of sound in air, V is the air velocity in the exhaust passageway, and F is the fan blade pass frequency when the motor is rotating the fan at an operational speed.
 18. A heater venting system as set forth in claim 12 wherein the shunt is oriented such that the closed end is above the open end to prevent liquid from collecting in the shunt.
 19. A heater venting system as set forth in claim 12 wherein the shunt comprises a first shunt, the heater venting system further comprising a second shunt, the second shunt including a pipe section having a shunt chamber, the shunt chamber of the second shunt having an open end, a closed end, and a shunt chamber length extending from the open end to the closed end of the second shunt, the second shunt being coupled to the exhaust pipe such that the shunt chamber of the second shunt is in fluid communication with the exhaust passageway via the open end of the shunt chamber of the second shunt and such that the shunt chamber of the second shunt extends generally laterally from the exhaust passageway, the shunt chamber length of the first shunt being of a first length to attenuate a noise of a first frequency, the shunt chamber length of the second shunt being of a second length to attenuate a noise of a second frequency, the second length being different from the first length, the second frequency being different from the first frequency.
 20. A heater venting system as set forth in claim 12 wherein the shunt length is less than ten inches.
 21. A method as set forth in claim 8 wherein the first noise includes an objectionable tone, the chamber length of the first shunt being nλ/4±0.1(λ/4), and the chamber length of the second shunt being nλ/8±0.1(λ/8), where n is any odd integer and λ is the wavelength of the objectionable tone. 